Brenda - our cat would slip out, given the chance (she's 13, but very lively and yes, she's an inside cat). She doesn't go far, but I remember when she went under our 16'x19' deck, and there's no way we could get her out until it got cold or she was hungry! If that was the middle of the night, we were "Stuck". I don't want to trust to Providence on any camping trips! I'd be worried the entire time, and would not enjoy myself.
Here, at home, we don't let her out either - there are coyotes in the area and they've been known to prowl our trailer park!